Gameplay of Hearthstone

Hearthstone is a digital collectible card game released by Blizzard Entertainment in 2014, available for Microsoft Windows and macOSPCs and iOS and Androidsmartphones. The game is free-to-play, with players gaining in-game currency and card packs via winning matches and completing quests, while real-world money can be spent to acquire additional card packs and cosmetic items. The game has been critically well-received and financially successful, estimated to generate over $20 million per month as of 2015.[1]As of May2017, Blizzard has reported more than 70 million Hearthstone players. Blizzard has continued to expand the game with the addition of multiple expansions, adventures and game modes.

Gameplay

Hearthstone is a digital-only collectible card game that revolves around turn-based matches between two opponents using pre-made decks of cards.[2] Players can choose from a number of game modes, with each offering a slightly different experience. Players start the game with a limited collection of basic cards but can gain rarer and more powerful cards through purchasing packs of cards or as rewards from specific game modes. Hearthstone is purposely designed to exclude card trading, while allowing players to disenchant unwanted cards into a quantity of arcane dust that can then be used to craft new cards of the player's choice. Players customize their decks with any gained cards to improve their chances of winning and gaining further rewards.

Hearthstone is free-to-play, only requiring the player to download the game client for their computer or device after setting up a free Battle.net account; supporting the ongoing development of the game comes from micropayments. Players can earn in-game gold by winning play mode matches and completing daily quests, such as winning a certain number of matches while in play mode with a particular hero class. A player can have up to three active daily quests, which carry over until completed or the quest is declined by the player; a new daily quest is given once a day. Gold can be used for booster packs, entry tickets for arena and access to adventure wings.[3][4] Alternatively, players can spend real money to purchase these items directly, and can buy exclusive card back skins and alternate heroes.[2] During the week before the Journey to Un'Goro expansion released in April 2017, Blizzard temporarily added daily log-in rewards that included gold, arcane dust for card crafting, card packs, and individual cards.[5]

Hearthstone is set within the Warcraft universe, with its characters, spells and locations drawing mostly from existing lore. The game has a few original characters like Sir Finley Mrrgglton and Morgl that were later added to World of Warcraft.

Matches

Each Hearthstone match is a one-versus-one battle between two opponents. Gameplay in Hearthstone is turn-based, with players taking turns to play cards from their hand, limited by available mana, that include casting spells, equipping weapons, summoning minions to do battle on their behalf or replacing a player's chosen hero with a Death Knight hero.[6] Games may be between two players, or one player and one computer-controlled opponent.

Each player is represented by a 'hero', a character from Warcraft lore representing one of nine specific classes. The classes are defined by their unique hero power that can be used once-per-turn in matches (some cards may affect the number of times this can be used), and the selection of class-specific cards that the player uses to construct the hero's deck. The nine available classes, along with their hero names, are Mage (Jaina Proudmoore, Medivh or Khadgar), Priest (Anduin Wrynn or Tyrande Whisperwind), Warlock (Gul'dan, Nemsy Necrofizzle or Mecha-Jaraxxus), Paladin (Uther the Lightbringer, Lady Liadrin or Arthas Menethil), Warrior (Garrosh Hellscream or Magni Bronzebeard), Druid (Malfurion Stormrage or Lunara)[7], Hunter (Rexxar or Alleria Windrunner), Rogue (Valeera Sanguinar or Maiev Shadowsong) and Shaman (Thrall or Morgl the Oracle).[8] In some of the game modes, such as Adventures or Tavern Brawls, the player may play or face against a non-standard hero or enemy with a pre-built deck and a unique hero power which are not available outside of these game modes.

At the start of the match, each player draws cards from their respective deck of thirty cards after it is shuffled. One player is randomly selected to go first. The first player draws three cards while the second player draws four. Players have the option to mulligan any of the cards in their starting hand, with replacements coming from the rest of their deck. At the end of the mulligan, the second player gets a card called "The Coin," a spell that gives a mana crystal at any point during a player's turn. Despite the second player's two card advantage, game director Ben Brode claims that on average the first player has a 3% higher chance to win, and Ars Technica's analysis of three professional tournaments found only an insignificant advantage for the first player.[9] Each player subsequently starts with no existing mana crystals.

Players then proceed to alternate turns. At the start of each turn, all empty mana crystals for a player are refilled and they gain a new filled mana crystal, up to a maximum of ten. If a card with an Overload keyword is played, this will limit the number of available mana crystals during the following turn. The player then is required to draw a card from their deck; if they have run out of cards, their hero takes an increasing amount of damage on each successive draw, called Fatigue. During their turn, each player may choose to play any of their cards, use their hero power, or direct attacks against the opposing hero and their minions. Nearly all cards and hero powers cost a number of mana points, and the player must have at least that many filled mana crystals to perform that action, which then drains those crystals until their next turn. Unlike card games like Magic: The Gathering, the opposing player has no means to interrupt or counter the current player's action during their turns, though some card effects can be triggered by the other player's actions and are automatically handled by the game. Each player's turn is limited by a timer, pausing only during card animations; the player is warned when this countdown is nearly over by displaying a burning rope. If the countdown ends before they complete their turn, they forgo any further actions and their turn ends. Players can end their turn at any time before this, and the game will indicate to the player when they have exhausted all possible actions for a turn to allow them to end it early.

Heroes typically start a match with 30 health points. Some cards and hero powers allow the hero to gain a number of points of armor, with no limit, or heal up to the maximum health for their hero. Any attack damage dealt to the hero first depletes the armor value and it must reach zero before damage can be done to the hero's health. A match is concluded when one or both players have reached zero health, when a player chooses to concede or when the maximum number of turns, 45 turns for both players, is reached. Completing a match will grant each player experience for that hero class. The amount of experience gained is dependent on the game mode, whether the opponent was computer or player controlled, how many turns the game lasted and whether the match was won. Leveling hero classes grants the player access to additional basic cards up to level 10 for that hero or golden versions of Basic cards past level 10; once all heroes are level 60, the player will have collected all golden versions of Basic card set.

Each match takes place on a randomly selected battlefield, representing the board on which the game is played. Several of the battlefields are inspired by the lore of Warcraft or based on the game's expansions. Each battlefield features its own design and many interactive elements, but the gameplay is in no way affected or determined by battlefield selection; the differences are purely cosmetic. Around the battlefield are the game's important user interface elements, which are each player's hand, deck, hero portrait, hero power, mana crystals, the log of recent cards played and actions taken and each hero's summoned minions. At any time, players can select or mouse-over face-up cards to get more details on their effects including definitions of keywords. The player may use six pre-set emotes to communicate with their opponent. Text-based messages may be exchanged with the opponent if they are part of the player's Battle.net friends list. Players may observe and send messages to their Battle.net friends while the friend is playing a match.

Card categories

Cards are the main substance of Hearthstone, representing the abilities, characters and effects each player is able to make use of during the match. Cards fall into four broad categories: summon cards to bring minions into the game, spell cards that create some type of immediate effect, equippable weapons that enable the hero character to attack directly and hero cards that transform the basic hero into a different one. All cards have a mana cost that must be provided by the available mana the player has for that turn.

Once summoned, minion cards each have an attack and a health value; when a minion attacks a target, it will deal its attack value to that target's health, and if it is attacking a minion, it will take damage based on the defending minion's attack value. A minion's health does not regenerate at the start of the player's next turn, so minions can be destroyed after taking smaller amounts of damage over several turns. Minions normally cannot attack the turn they are put into play, and once in play, they can normally attack once per turn. Some keywords affect the behavior of minions from these basic rules: examples include those with "Taunt" that must be destroyed before any other minion without taunt or the opposing hero can be attacked, those with "Charge" can attack the turn they are brought into play, and those with "Windfury" can attack twice per turn. Other keywords define actions to be taken at specific events: minions may have "Battlecry" events that only trigger when they are played from a player's hand, "Deathrattle" events that occur when the minion is killed, and many more. Tooltips are provided for all keywords, and interactions of minions and their keywords often crucial to success in matches.

Minion positioning on the game board can be important as some minions and spells will affect adjacent minions. Minions may belong to a specific tribe such as "Beast", "Demon", "Murloc", "Pirate", "Mech", or "Elemental", as labeled on the card. Some cards can be influenced by or can influence minions in play or in the player's hand that belong to that specific tribe.

Spell cards can be used for example to cause damage to the opposing hero or their minions, apply buffs or debuffs to minions or draw additional cards from their deck. As a digital-only game, some of Hearthstone's spells can also be used by the player to pull in cards from the entire available Hearthstone library that meet certain requirements, even if they do not own these cards. Spell effects may last for only a turn or may be permanent on the card it affects as long as it stays in play. Buffs or debuffs can be silenced to remove all effects from a card.

Equippable weapons have an attack value and a durability value. When equipped, the player can direct their hero to attack as if they were a minion; the hero's attack value will be that of the weapon, and the hero will take damage if he attacks a minion. The weapon's durability drops by one after the attack, as well as through other card effects, and if it drops to zero, the weapon is unable to be used to attack and is usually destroyed. Usually, weapon attacks can only be used once a turn.

Hero cards, introduced in the "Knights of the Frozen Throne" expansion, transform a player's hero into a Legendary hero with a different hero power, which is related to the replaced hero's power.[6]

At times, Blizzard has altered the attributes and effects of certain cards after their release based on observations from gameplay, to prevent unforeseen game-breaking combination attacks or effects that would be over-used by players. Many of these changes are "nerfs", reducing the effectiveness of the card's ability, while there have also been some "buffs"/"revamp" that improve cards. These changes are retroactive, affecting all existing cards owned by players.[10][11] Normally when a card has been changed, players are offered a full refund of dust crafting cost if the player chooses to disenchant the cards within two weeks of the change.[12]

Decks

In all game modes except Arena, some parts of Adventure mode and a few of the weekly Tavern Brawls, the player does battle using a constructed deck of 30 cards selected from the player's collection, using a mix of neutral cards available to all classes and specific class-based cards available to the chosen Hero. Each deck can only feature two of each card and only one of each Legendary rarity card. Legendary cards are the rarest cards in Hearthstone and are usually based on unique characters within the Warcraft universe. Arena play features no such limitations on the number of regular or Legendary cards but requires players to play using a new deck chosen from a series of randomly generated selections.

After release, Blizzard has adopted a "Year" moniker to identify when expansions have been retired from Standard format; the first, "Year of the Kraken", lasting from April 2016 to March 2017, retired the "Curse of Naxxramas" and "Goblins vs. Gnomes" expansions, while the "Year of the Mammoth", starting in April 2017, retired the "Blackrock Mountain", "The Grand Tournament" and "League of Explorers" sets. The "Year of the Mammoth" Standard set also moved some Classic cards to the "Hall of Fame" set that is not playable in Standard but still can be obtained through card drops and available to play in Wild format.[5]

Since the introduction of the "Year of the Kraken", decks are built either to the Standard or Wild format. Standard decks may be played in either format, but Wild decks can only be played in the Wild format. Wild format decks can use any cards within the Hearthstone library, limited by standard deck construction rules. Alternatively, the Standard format limits cards to those in the Basic and Classic set, and from any newer expansions (those released from a year to two years prior). Cards from previous expansions cannot be used except in Wild formats, nor could card packs or these expansions be purchased (except through the battle.net shop), though players could still craft these cards or complete purchased adventures to own them. The Standard approach was added to help improve competitiveness for new players while helping to maintain a dynamic metagame.[13]

The construction of a player's deck is a key strategic element in the game, determining which cards are available during a match. The game gives each player a pre-made deck for each Hero using the game's Basic cards, allowing them to get a quick start in the game. The game provides a few deck recipes for each hero that are based on various successful deck archetypes and it populates the deck with the cards a player already owns. Hearthstone offers a deck construction helper to guide new players on selecting a good range of card types and values, or to finish off decks that are partially completed.[14] The player has the ability to create up to eighteen custom decks, increased from the nine initially available before the release of the Whispers of the Old Gods expansion.[15] With a June 2017 patch, players can share the composition of their deck with others via a unique code generated in-game.[16][17]

Card library and crafting

On release, the game consisted of the same Basic set of cards that all players begin with and earn through leveling up all the individual heroes. All additional cards are generally gained by winning or buying card packs in the game; each card pack consists of five random cards.[2] On Hearthstone's release, purchased cards and packs would be from the Classic set, while with the release of each expansion or adventure, cards and packs from that expansion could also be gained. As of August2018, there are 1729 unique collectible cards in the game, with more planned to be added in the future through expansion packs.[8] Not all cards in the game are collectible in a player's library, as some cards are created as effects from other cards or spells, while others are unique to a specific Adventure or Tavern Brawl game mode. The former are comparable to Magic: the Gathering's tokens. Each card is classified as neutral or specific to one of the nine classes; with the introduction of Mean Streets of Gadgetzan, tri-class cards were added, meaning the card can be used by three different classes.[18]

Players can purchase card packs within the game or through Blizzard's storefront. Players can purchase decks from any of the current available expansions for Standard play as well as the Basic set. A single pack costs 100 gold coins (in-game currency); alternatively, players can purchase multiple packs at a time using real-world money with volume discounts; for example, two packs cost $2.99 (€2.99 or ₤2.99) while 60 packs cost $59.99 (€69.99 or ₤59.99).[19] All cards in a card pack are randomly selected from the given card pack expansion with one card guaranteed to be of Rare or higher rarity. A Legendary card is guaranteed to be in one of the first ten packs of an expansion opened by a player; subsequently, the regular card appearance rate occurs. A player is guaranteed to not open a Legendary card that they already own, unless they already own all Legendary cards in a card pack's set.[20]

Additionally, players can use the crafting system to create new cards. The system uses arcane dust to craft specific cards. Arcane dust can be obtained by destroying existing cards, from arena mode rewards or from the end of season rewards. Because cards can be used in more than one of the player's constructed decks, a player only needs a maximum of two copies of any regular card or one copy of a Legendary card in their collection, and the game can automatically convert extras into arcane dust. The crafting system was created as an alternative to the player card trading prevalent in trading card games such as Magic: The Gathering,[21] with no plans for cards to be traded between players.[22] Similar to the foils found in physical collectible card games, Hearthstone features golden cards that are special versions of regular cards featuring a golden border and unique animations. These cards are less common than the regular ones and are worth more arcane dust. Golden cards differ from their regular counterparts purely cosmetically and are intended to allow players to show off their special cards to others.[23]

Game modes

Five game modes are available to play in Hearthstone. Matches in all modes except for Solo Adventures count towards quest completion; Duels initially did not count towards quest completion except during limited periods, but a game update in June 2017 allowed these matches to add another way to complete the daily quests.[16][17]

Play mode allows players to match up against human opponents of similar skill. Players can choose to play casual 'friendly' games, or take part in the ranked play system, earning ranks to reflect their skill and standing within the community over month-long seasons. Ranked play features two separate tiers: 25-1, and Legend, which employs a visible leaderboard for individual player rankings within the player's region. Winning a match earns stars, which are required to proceed to the next rank, while losing matches can lose stars and lead to demotion of rank, though stars cannot be lost in Ranks 25 to 21. Prior to February 2017, there were two "floors" in this ranking system, where players could not be demoted below once achieved, at Rank 20 and at Legend. A patch in February 2017 introduced three additional "floors" at Ranks 15, 10, and 5 in response to player criticism of the difficulty in moving up ranks with the shortness of each monthly season.[24] All ranks are reduced at the start of a new season. Participation in ranked play can earn players special cosmetic rewards. Blizzard has awarded a new card back at the end of each season for reaching at least Rank 20, with bonus rewards such as golden cards and arcane dust for reaching higher ranks.[25] After the release of WOG, Play mode matches can either use the Standard or Wild format. Standard format restricts decks to Basic and Classic cards, as well as any cards from sets released in the last two calendar years. Wild format allows decks to be made with no restrictions.[26] On debut of this format in 2016, Standard decks cannot use cards from Naxx or GvG, since both were released in 2014.

Solo Adventures are single-player modes against computer-controlled opponents that are either Practice matches or Adventures. In Practice mode, players can learn the basics of the game against easier opponents that only use basic cards in their decks, or more difficult ('expert') opponents that use a larger pool of cards. Players can also choose which class to play against. In Adventure mode, the player attempts to defeat bosses to unlock new cards.[27][28] The boss encounters feature unique dialogue elements.[29] For example, "Curse of Naxxramas" was divided into five sections ("wings"). Each section was purchasable as a one-time transaction for 700 gold or real-world equivalent, with future sections locked until the previous sections were completed.[30][31] Bundle discounts are offered if all remaining locked sections are purchased at one time using real money.[32] After an adventure is removed from Standard format, it is unavailable for players to purchase. Thus at the release of WOG, Naxx was removed from the store.[26]

Arena mode allows the player to select one of three random heroes and draft a deck of 30 cards by choosing between three random cards at a time. Players use their drafted deck to compete in a series of games against other arena players, generally matched against decks with an equivalent win-loss record. Each arena run lasts until the player has reached three losses or twelve wins, at which point they earn rewards determined by the total number of games won. While constructed decks have limits on the number of copies of the same card in a single deck (two), arena decks have no such limits.[33] Access to a single Arena run (drafting a deck and playing until it reaches the win or loss limit) requires a purchase of an Arena Ticket which costs either 150 gold or real-world money of $1.99 (€1.99 or ₤1.99). Prior to the "Year of the Mammoth" updated in 2017, Arena mode ran under the Wild format, allowing any card to be potentially offered during the deck construction process; with the 2017 update, Arena mode will be limited to Standard format, and will also see altered card distributions from normal play, making neutral cards less common and increasing the chances for the more rarer class-specific cards to be offered during Arena deck construction.[34]

Tavern Brawl mode features one-on-one matches with another player. These commonly are competitive matches to defeat the other player, but some matches have featured cooperative goals such as jointly defeating a powerful minion. These matches force players to deal with a set of specific guidelines, which change on a weekly basis.[35] Playing matches in this mode is restricted to players that have at least one level 20 hero character. The reward for the first time a match is won during a weekly brawl is normally one Classic pack.

Duels, also referred to as "Friendly Play" and "Friendly Challenge",[36] allow players to challenge friends on their Battle.net friends list in unranked matches.

Additionally, the game features a tutorial that is a limited starting experience designed to introduce players to Hearthstone, in which the player is matched against a series of computer-controlled opponents that includes dialogue elements. The tutorial may be played only once by an account per Battle.net region.

Players gain a quest daily, and can store up to three quests, that can be completed to earn in-game gold or other rewards. The requirements of these quests are based on cumulative performance in matches, typically requiring the player to win multiple matches with certain hero classes, destroy a number of minions, damage opposing heroes, observe a friend winning a game, playing a certain number of a particular type of card or other similar tasks. Progress towards completing quests typically can only be achieved through game modes with random matchmaking (Play or Arena), but Blizzard has offered periods where other play modes, such as duels, count and in June 2017 made duels always count for quest completion. A player can "reroll" one quest once per day to get a different one. With the "Year of the Mammoth" introduction, Blizzard has added log-in rewards and other meta-game elements occasionally.[5]

Game regions

Hearthstone offers play in four different geographical regions: Americas, Europe, Asia and China. Players can only compete and communicate with other players within the same region. While each player is by default assigned to a region loosely corresponding to their registered country of residence, players are able to switch regions within the Battle.net launcher, allowing them to play against those from other regions if they wish, although players from other regions are unable to select the China region for play on the same device. Each region holds a separate profile for each player, and it is not possible to transfer cards, gold or other details between regions. Players wishing to play in a new region must begin the game from the start, including replaying the tutorial and restarting their card collection.[37]

Expansions and adventures

Blizzard has expanded Hearthstone roughly three times a year by the addition of expansions and adventures. Each expansion presents more than 100 new cards to Hearthstone developed around a theme or gameplay concept; once released, players can purchase or win card packs with cards from the available expansions to add to their library. Adventures represent fewer new cards, typically a few dozens, which are only gained by winning specially designed matches against computer opponents in the single-player mode. Access to an adventure requires payment with in-game gold or real-world money. All adventures have multiple "wings" that must be completed; each wing can be purchased separately for 700 gold or $6.99 (€6.99 or ₤6.99), with a lower cost if buying multiple wings at once.

Since the "Year of the Mammoth", which began with "Journey to Un'Goro" in 2017, there will be no more adventure releases. Instead, the game will include freely-available single-player missions, similar to those in adventures, to earn card packs from that expansion.[5] As of August 2018, there have been nine expansions and four adventures, while there is one more expansion planned for 2018.

↑ Nine cards originally in Classic were moved to the Hall of Fame set that is not playable in Standard.

↑ Four Reward cards were originally included and given to players on completing certain tasks. Two Reward cards were not playable in Standard in the Year of the Kraken; with the Year of the Mammoth, all Reward cards were moved into the Hall of Fame set.

↑ The Hall of Fame set consists of cards that have been rotated out of the Classic set. Because of the sporadic additions to the set, there are no definite release or removal dates.[38][39]

Curse of Naxxramas

The adventure "Curse of Naxxramas" was announced on April 11, 2014,[56] and then was released on July 22. It includes 15 bosses and nine class challenges that together awards 30 cards, which includes six legendaries, and an exclusive card back if all heroic bosses are defeated.[28] "Curse of Naxxramas" was developed to focus on a specific gameplay mechanic, with the team settling onto exploring the design space around the "deathrattle" keyword. This led to the narrative of the player having to explore a location filled with ghosts and undead creatures as to take advantage of deathrattle effects.[57] Since it was a single-player adventure, the team also developed bosses that would be far different from typical human opponents, including some boss characters that would break the fundamental rules of the game. Lead artist Ben Thompson said that they made it felt like winning against these bosses was something that the player earned, as well as helping the player to learn new tricks they could use in regular play modes.[58]

Goblins vs. Gnomes

The expansion "Goblins vs. Gnomes", was announced at BlizzCon on November 7, 2014, and then it was released on December 8. The expansion includes 123 cards found in its specific card pack. Pricing for the packs are the same as Classic packs.[59] "Goblins vs Gnomes" was the first large expansion, and rather than roll out cards as they did with "Curse of Naxxramas", they felt their goal with this "was ‘let’s make a bunch of cards that will really go in and just blow up the meta all at once,’ and we’ll see how it goes, and maybe that’ll affect how we do things in the future," according to Chu. A central theme was designed around the "Mech" tribe cards that would interact with cards that represent goblins and gnomes.[60]

Blackrock Mountain

The adventure "Blackrock Mountain" was announced at Pax East on March 6, 2015 and the first wing was released on April 2; the other four wings were opened weekly thereafter. It includes 17 bosses and nine class challenges that together awards 31 cards, which includes five Legendary cards, and an exclusive card back if all heroic bosses are defeated.[43] "Blackrock Mountain" was designed as to help support players that wanted to construct dragon-themed decks. Dragon cards in Hearthstone are generally expensive to cast and thus only appear in the latter part of a match, making such decks weaker in the opening rounds. With "Blackrock Mountain", the team introduced cards that interacted with dragon cards, such as by having special effects when a minion is summoned while having a dragon card in hand.[61]

The Grand Tournament

The expansion "The Grand Tournament" was announced on July 22, 2015, and was released on August 24; the set includes 132 cards found in its specific card pack, which costs the same as previous card packs.[62][63] "The Grand Tournament" was developed with a new card mechanic for minions called "Joust" which has combat between a minion with Joust with other minions based on the casting cost of the minions, rather than their attack and health. Donais noted that while this also created a central theme for "The Grand Tournament" expansion, it also served to help combat "aggro" decks—decks filled with low-cost minions that could be quickly deployed—which at the time of the expansion's release, were extremely popular and found to be discouraging to many players. "The Grand Tournament" also introduced the "Inspire" mechanic for minions, which would create some effect for the minion each time the player used their Hero power, often including cumulative effects over several turns. Donais said the Inspire keyword came about looking at how to interact with Hero powers better, and while Inspire-based cards could be slow and at risk, could have great payoffs if used properly.[64]

League of Explorers

The adventure "League of Explorers" was announced at BlizzCon 2015 on November 6, 2015, and the first wing was released on November 12; the other three wings were opened weekly with a week-long break after the second wing. It includes 13 bosses and nine class challenges that together awards 45 cards, which includes five legendaries, and an exclusive card back if all heroic bosses are defeated.[65] "League of Explorers" was the team's first attempt to craft a narrative that allowed Hearthstone to stand on its own from the Warcraft universe even though it may still borrow concepts from it from time to time. The adventure borrows from dungeons in desert locations within World of Warcraft but transform the experience to be one of an adventuring archaeologist, and the challenges were more themed around puzzles and traps that the dungeons would present rather than just boss characters. Central to "League of Explores" was the new "Discover" mechanic, which when activated would have the game randomly select up to three cards with specific characteristics from all available game cards, allowing them to select one card to put into their hand. This mechanic was introduced to provide contrast to decks that focused on card draws, which they found out tend to be played in the same manner over time. The Discover mechanic allowed decks to be more random but provide some player decision for on-the-spot judgement calls depending on the situation.[66]

Whispers of the Old Gods

The expansion "Whispers of the Old Gods" was announced on March 11, 2016, and was released on April 26; the set includes 134 cards found in its specific card pack, which costs the same as previous card packs.[67][68] "Whispers of the Old Gods" was based on creating a theme around mysterious and dark Lovecraftian horror, such as Cthulhu, to contrast to the high adventure and excitement that they had designed with "League of Explorers". This concept of crafting powerful god-like characters let them brainstorm on wild ideas for cards that may seem overpowered for the game but that would fit the theme. Central to the expansion is the Legendary "C'Thun" Old God card, which can be buffed by effects from sixteen other cards, disciples of C'Thun, that were part of the expansion, regardless of where the C'Thun card was currently at. Donais explained this helped to create a "sense of dread" in opponents that fit the theme they wanted. Because of this, all players received the C'Thun card and one of the disciple cards for free once this expansion was released. "Whispers" also allowed the designers to take old favorite cards and make "corrupted" versions of them within the flavor of the theme.[69]

One Night in Karazhan

The adventure "One Night in Karazhan" was announced on July 29, 2016, and the first wing was released on August 11; the other three wings were opened weekly thereafter. There are four wings along with a free prologue mission that awards two cards. Kara includes 13 bosses and nine class challenges that together awards 45 cards, which includes five legendaries, and an exclusive card back if all heroic bosses are defeated.[70] "One Night in Karazhan" is based on a popular game location in World of Warcraft, featuring an abandoned mage's tower that is often used for a dungeon raid. The adventure features eleven boss characters that are also in the World of Warcraft raid of the tower. The team had designed the concept of this expansion alongside "Curse of Naxxramas" early in Hearthstone's post-release and was considered to be their first adventure, but they ultimately used Naxxramas, as Karazhan was being used for other activities by teams within Blizzard at that time. Instead, when they looked towards designing it, they found Priest decks had difficulty in staying current with the meta-game, so several of the cards introduced with this set were to help make the Priest a more viable class with the shifts in popular decks.[71]

Mean Streets of Gadgetzan

The expansion "Mean Streets of Gadgetzan" was announced at BlizzCon 2016 on November 4, 2016, and was released on December 1; the set includes 132 cards found in its specific card pack.[72] "Mean Streets of Gadgetzan" was originally envisioned to have the spirit of "cops and robbers", according to designer Matt Place and art director Ben Thompson, but the idea transformed into squarely focusing on the crime aspects, and treating the narrative as three principle mafia-like crime families vying for control of the city of Gadgetzan along with a number of small-time criminals that work as hired hands. The nine hero archtypes were divided into sets of three that each worked for a different family, which led to the creation of tri-class specific cards. Each of the three families were given a central mechanic theme: the Grimy Goons buff cards that in a player's hand, the Jade Lotus improve new Jade Golem cards the more they are played, and the Kabal use Discover cards to use certain cards from outside a player's deck. The set includes Legendary cards that represent the leader of each family.[73]

Journey to Un'Goro

The expansion "Journey to Un'Goro" was announced on February 27, 2017, and was released on April 6;[74][50] it contains 135 cards found in its specific card pack. "Journey to Un'Goro" is based around a pre-historic theme and introduces dinosaurs and the Elemental tribe, including retroactively making some previously released minions as part of the tribe. It introduces Legendary spells with the "Quest" keyword, which award a unique minion or spell when the conditions of the quest are fulfilled. If a Quest card is in the player's deck it will be put into the player's opening hand, although players are allowed to mulligan it, and it must be put into play before the player can start completion of that quest. The expansion also adds the "Adapt" keyword to some minions and spells, which allows the player to select a buff to apply to one or more minions.[51][75]

Knights of the Frozen Throne

The expansion "Knights of the Frozen Throne" was announced on July 6, 2017 and was released on August 10.[6] The set's theme is about the frozen wastes of Northrend and Icecrown Citadel, and the set features the game's heroes embracing the power of the Undead Scourge, becoming Death Knights in the service of the Lich King. The expansion features the introduction of hero cards, an entirely new card type which transforms the player's hero and hero power along with varying unique effects, and the Lifesteal mechanic. It features 135 cards and includes adventure-like missions for single-players, featuring a narrative leading to a boss fight with the Lich King that can reward one random Legendary death knight card, multiple card packs and for dedicated players an alternate hero for Paladin - Arthas. The expansion introduced the Lifesteal keyword; when minions or spells with this keyword deal damage the controlling hero is healed by the same amount.

Kobolds & Catacombs

The expansion "Kobolds & Catacombs" was announced in November 2017 during BlizzCon 2017 and was released on December 7, 2017. The general concept of the expansion was around the idea of dungeon crawls from role-playing games.[76] Its 135 cards are themed around exploring old catacombs under Azeroth and uncovering valuable treasures. Among the cards include Legendary weapons for each class that includes classes that have never had weapons before, Spellstone cards that require the player to achieve certain objectives in-game to upgrade the card, "Unidentified" item cards that offer a random effect alongside a known effect, and cards with a "Recruit" keyword that allow the player to summon minions directly from their deck that meet the card's requirements. All players received the Legendary minion Marin the Fox a month ahead of time and after the set was released, one random Legendary weapon card.[77] Earlier in 2017, Blizzard had planned for this set's theme to be around Warcraft's Blingtron robots and would have been known as "Blingtron's Lootapolooza". While this theme still centered around dungeons and loot, they decided that the set would have better flavor and easier art to design by switching the theme to kobolds; however, this decision came after they started some of the promotional material, so some of the art includes Blingtrons.[78]

The expansion introduces a new single-player mode called a "Dungeon Run", a roguelike-style format. The goal for the player is to complete battles against eight boss characters randomly selected from a pool of 48 that become more progressively difficult. The player starts by selecting a class, which gains them a small deck of cards for that class. For each boss they defeat, the player gains additional starting health in the next battle, a choice of three sets of three randomly selected cards around a theme, and in some cases, a unique treasure card otherwise not available in the normal game modes. Should the player be defeated by a boss, that run is ended, and the player must start a run anew. Cards from the Dungeon Run do not become part of the player's library, though players can earn card packs through quests involving Dungeon Runs, and can earn a unique card back by completing runs with all nine classes.[76] The idea for the Dungeon Run is based on the expansion's theme and the mode works as an optional single-player experience independent of the card collection of the player.[76]

The Witchwood

TheWitchwood was announced in March 2018 as the first expansion in the Year of the Raven and was released on April 12, 2018.[79] It is themed around a spooky forest next to the cursed city of Gilneas from Warcraft. The expansion adds two new keywords; "Echo" cards can be played as many times on a turn as long as the player has the mana to pay the cost, while minions with "Rush" can immediately attack the opponent's minions on the turn they are summoned. The set also features cards that give a special effect if a player's deck only contains even-cost cards or odd-cost cards, effectively limiting players to only half of their card collection in assembling decks to take advantage of these cards.[80][81]

The expansion adds a single-player mode called "Monster Hunt", an evolved version of Kobolds & Catacombs's "Dungeon Run", which became available to play two weeks after the expansion was released.[82][83] In the "Monster Hunt", players pick between four unique heroes that have a unique hero power and unique cards. After defeating each encounter, players pick between three sets of cards to improve their deck and occasionally earn special cards or an ability to improve their hero power; there are over 45 encounters. Players can earn a unique card back, which requires defeating eight bosses of increasing difficulty, with each of the four heroes, and then defeating the final boss, Hagatha the Witch.[84]

The Boomsday Project

The Boomsday Project was announced in July 2018 and was released on August 7, 2018.[85] The set focuses on "Mech" characters and abilities, similar to Goblins & Gnomes, and is themed around the minion Dr. Boom that was introduced in the former set, having set up a villainous laboratory in the Netherstorm. The set introduced the new "Magnetic" keyword, which allows a player to use a card as a buff if the "magnetic" card is played to the left of a mech, and as a stand-alone minion otherwise.[86] The Magnetic mechanic had originally been designed as "Modular", whereby playing a card would either allow the player to select from two effects: playing it as a spell atop a mech, or as its own minion. The developers found this could lead to long turns if a player's deck primarily consisted of such cards, to the point they had been ready to cut the keyword and release the set otherwise. However they found a solution through the user interface, by letting the player make the choice at the same time as playing the card if they placed it in a specific location near a mech.[87]The Boomsday Project is also the first expansion to have new legendary spell cards for each class.

The set also includes a single player mode called the Puzzle Lab, which presents more than 100 Hearthstone-based puzzles where players are given a pre-determined game state and must attempt to complete a given objective. The puzzles are split among these four different objectives: Lethal, where players must win the match during their turn; Mirror, which requires the player to match the minion battlefield on both sides; Board Clear, where the battlefield must be cleared of minions; and Survival, requiring the player to survive until the next turn. The Puzzle Lab was released two weeks after the expansion's release. Players who complete all the Puzzle Lab missions will be rewarded with a card back.[88][89][90]